Inkjet printing apparatuses have been widely used and commercialized as a computer-related output device and the like because their running cost is low and they can be downsized and easily compatible with color image printing using a plurality of color inks.
As an energy generating element which generates energy for discharging ink from the orifices of a printhead, some printheads use an electromechanical transducer such as a piezoelectric element. Some printheads generate heat by emitting an electromagnetic wave from a laser or the like, and discharge ink droplets by this heat generation. Some printheads heat liquid by an electrothermal transducer having a heating resistance element.
Of these printheads, an inkjet printhead which discharges ink droplets by using heat energy can print at high resolution because orifices can be arrayed at high density. A printhead using an electrothermal transducer as an energy generating element can be easily downsized. This printhead can fully utilize advantages of the IC technology and microfabrication technology which are progressing rapidly and improving reliability in the latest semiconductor industry. In addition, this printhead facilitates high-density packaging and reduces the manufacturing cost.
These days, nozzles for discharging ink are arrayed at high density using photolithography in order to print at higher resolution.
Procedures to fill such a printhead with ink in an early stage will be explained with reference to FIG. 14.
In a printer of FIG. 14, a suction cap 207a of a recovery unit covers the nozzle face of a printhead 201 to tightly close the printhead 201. Then, a suction pump communicating with the cap sucks. The suction by the suction pump sets a negative pressure in the ink channel of the printhead 201 to discharge ink from nozzles to the cap. At the same time, bubbles in the ink are also discharged from the nozzles, thereby removing bubbles.
In this bubble removal by suction recovery, bubbles in the printhead can be removed, but ink is wasted in the recovery operation.
Japanese Patent Laid-Open No. 2000-301737 discloses a technique for solving the problem of suction recovery. In Japanese Patent Laid-Open No. 2000-301737, the internal pressure of an ink chamber in a printhead is reduced by a pressure reducing pump via an exhaust tube connected to the top of the ink chamber, releasing bubbles in the ink chamber into air. At the same time, ink is supplied into the ink chamber to raise the liquid level. A float member lower in specific gravity than ink is arranged. As the liquid level rises, the float member also rises to automatically close the exhaust tube so as not to discharge ink from the exhaust tube. This structure enables the bubble removal operation in the ink chamber without wasting ink.